Modern vehicles frequently employ electromechanical control systems that control movement of access control members such as doors, trunk lids, liftgates, moonroofs, etc. between open and closed positions as a convenience to a user of the vehicle. For the safety of the user, vehicles also frequently include an obstruction detection system that can detect the presence of the user or an object in the path of movement of the access control member. In this manner, for example, the vehicle is able to prevent injury to the user or damage to an object in the path of movement.
Most conventional obstruction detection systems rely on contact with the user or object to halt movement of the access control member. In particular, resistive anti-pinching strip sensors are located along the edge of the access control member and, when actuated through contact with an obstruction, cause the control system to reverse movement of the access control member. Contact based obstruction detection systems have a number of drawbacks. They are relatively expensive. They often have difficulty in identifying obstructions where the shape or orientation of the obstruction makes it difficult to adequately deform the sensor or where the material composition of the obstruction has limited friction. The performance of the systems can also vary over time as materials in the sensors age. Further, contact based obstruction detection systems do not result in action until contact with the obstruction has already occurred. Therefore, they provide limited comfort to the vehicle user that the user will not suffer an injury or damage to an object of the user. Some non-contact obstruction detection systems have been developed that project light and detect obstructions through interference with the projected light. Existing systems, however, suffer from a high level of inaccuracy (often failing to detect small obstructions and, at other times, incorrectly indicating the presence of an obstruction) and often resort to the use of relatively expensive sensors to limit the level of inaccuracy.